The present invention relates generally to an electrical connector and, more particularly, to an electrical connector for connecting a zero force insertion (xe2x80x9cZIFxe2x80x9d) pin grid-array (xe2x80x9cPGAxe2x80x9d) package to a circuit member.
A typical pin grid array package includes a silicon chip, a package including conductive and non-conductive components and a plurality of pins in a grid array depending downward from a bottom surface of the package. Conventionally, zero insertion fore electrical connectors for PGA packages include a plate-like base housing having a plurality of terminals arranged in the same grid pattern as the lead pins of the PGA package and a plate-like cover member having a plurality of through holes in the same grid pattern as the lead pins of the pin grid-array package, thus permitting the lead pins to be inserted in the through holes. The plate-like cover member is slidably positioned on the upper surface of the base housing.
The base housing and cover are slidably interconnected so that the cover is driven in a plane parallel to the underlying base housing between a first position in which the lead pins of the PGA package can pass through the through holes of the cover to reach the terminals mounted in the underlying base housing without requiring any insertion force to be applied to the lead pins and a second position in which the lead pins of the PGA package contact the terminals.
A variety of terminal structures have been proposed as appropriate for use in such sockets. Some such terminals are configured such that their contact portions engage the lead pins of a PGA package upon movement of the cover of the socket. Conversely, some terminals are configured such that the lead pins of a PGA package are brought to the contact portions of terminals.
Essentially all of the terminals have contact portions located in the terminal-receiving cavities of the base housing of the socket, and most have straight pin-like solder tails extending from the bottom of the base housing of the socket. These pin-like solder tails are inserted into through holes of a printed circuit board on which the socket is mounted, and are soldered to the printed circuit board.
The base housing typically has some type of drive mechanism formed thereon for slidably moving the cover over the underlying base housing. In some sockets, a cam is rotatably attached to one lateral side or end of the base housing, and the cam is adapted to be rotated with an associated handle, thereby permitting the cam axle to push or pull the cover over the underlying base housing. The handle may be rotated from a horizontal position in which it is parallel to the base housing to a vertical position in which it is perpendicular to the base housing. Alternatively, rotatable eccentric cams having a generally vertical axis of rotation are well known.
The demand for ever smaller electronic devices has driven the demand for smaller components that make up the electronic devices. However, customers also desire increasing performance from these smaller devices. Thus, component designers must continue to shrink their designs while still improving their performance and ease of use.
Despite the efforts of previous designers, electrical connectors for PGA packages still pose important problems. For example, when an eccentric cam member is employed, it is typically inserted from an upper surface of the cover toward a lower surface of the base housing. Therefore, the eccentric cam must be secured after this insertion. Moreover, it is conventionally necessary to initialize the axial positioning of the inserted eccentric cam member with a high degree of precision in order for the rotation of the eccentric cam member to slide the cover through a desired range of motion relative to the base housing.
Another problem with electrical connectors for PGA packages is a lifting up of the cover during operation of an eccentric cam member. That is, when the cover is reciprocatingly moved by the rotation of the eccentric cam member, the cover often has a tendency to move up and away from the base housing.
A third problem with conventional electrical connectors may be designated xe2x80x9cclatteringxe2x80x9d. The user experiences this clattering as a stickiness or roughness in the rotation of the eccentric cam member. Clattering may be caused by assembly errors, poor manufacturing tolerances, or other factors. Ultimately, the clattering can shift the cover out of its intended operating position to the extent that the lead pins of the package can not be inserted into the electrical connector with zero insertion force.
An additional problem with conventional electrical connectors is overtravel of the of the cover relative to the base housing. Overtravel means that the cover is moved past the first insertion position or, in the opposite direction, past the second engagement position. Overtravel can make the insertion or removal of the pin terminals of the pin grid array difficult. In extreme cases of overtravel, the pin terminals or the electrical connector may be damaged. Lateral movement of the cover relative to the base housing is a related problem with similar consequences.
The invention is an improved zero insertion force electrical connector for a pin grid array having an overtravel preventor which limits movement of the cover relative to the base housing. The overtravel preventor includes a recessed portion and a protruded portion, which is movably accommodated within the recessed portion over a range of motion having a first insertion position and a second engagement position as end points. The invention may also include a guide mechanism for limiting lateral movement between the cover and the base housing.
In a preferred aspect, the invention is a zero insertion force electrical connector for mounting on a circuit member and receiving a device having a pin terminal array. The electrical connector includes a base housing defining an axle hole and having a plurality of individual terminal receiving cavities arranged in a terminal-receiving cavity array generally corresponding to the pin terminal array. A plurality of conductive terminals are distributed throughout the cavities. Each of the terminals has a contact area configured for engaging a portion of a respective one of the pin terminals.
A generally planar cover is mounted on the base housing. The cover defines a cam follower surface and is movable relative to the base housing between a first insertion position and a second engagement position. The cover also defines an array of through holes generally corresponding to the pin terminal array for receiving the pin terminals in the through holes. An actuator is mated with the cover and with the base housing. The actuator includes an eccentric cam member having an axis of rotation which is generally transverse to the plane of the cover. Rotation of the eccentric cam member causes the cover to move relative to the base housing between the first insertion position and the second engagement position.
The invention also includes an overtravel preventor to prevent the actuator from moving the cover past the first insertion position or the second engagement position. The overtravel preventor includes two side walls and a recessed portion defined by one of the cover and the base housing, and a protruded portion formed by the other of the cover and the base housing. The protruded portion is movably accommodated within the recessed portion over a range of motion having at least two end points which correspond to the first insertion position and the second engagement position, respectively.
In another preferred aspect, the invention is a zero insertion force electrical connector which includes a base housing, conductive terminals and a cover mounted on the base housing upper surface, substantially as described above. The cover also includes a metal upper cam plate, an insulative molded plate and a metal stiffener. The metal upper cam plate is adjacent one end of the cover, and has an upper follower surface which defines an upper cam hole. An actuator having a n eccentric cam member which includes a rotary axle configured to engage the axle hole, and an upper cam surface configured to engage the upper follower surface. The actuator serves to slide the cover relative to the base housing between the first insertion position and the second engagement position is mated with the cover and the base housing. The molded plate defines an array of through holes generally corresponding to the pin terminal array for receiving the pin terminals in the through holes.
Overtravel protection is provided by an overtravel preventor including two side walls and a recessed portion defined by one of the cover and the base housing, and a protruded portion formed by the other of the cover and the base housing. The protruded portion is movably accommodated within the recessed portion over a moveable range of motion having at least two end points which correspond to the first insertion position and the second engagement position, respectively.
In yet another preferred aspect, the invention is substantially as described above, with the additional features of the metal upper cam plate having an upper follower surface which defines an upper cam hole, and the metal stiffener having a lower follower surface which defines a lower cam hole. Also, the metal upper cam plate has an upper follower surface which defines an upper cam hole, and the metal stiffener has a lower follower surface which defines a lower cam hole. The cam surface has an upper portion and a lower portion. The rotary axle is attached to a retaining member and includes positioning means for positioning the retaining member relative to the rotary axle. At least one of the cam surface upper portion, the cam surface lower portion and the metal upper cam plate includes engagement means for limiting movement of the cover perpendicularly away from the base housing upper surface which permit the actuator to rotate about the rotary axle and the cover to move between the first insertion position and the second engagement position.
In still another preferred aspect, the invention is an electrical connector substantially as described above, which also includes a guide mechanism with a grooved portion defined by one of the cover and the base housing, and a tongue portion formed by the other of the cover and the base housing. The tongue portion is movably accommodated throughout a predetermined range of lateral travel within the grooved portion.